Photoresists of alkali-soluble novolak resins and sensitizers such as those described in U.S. Pat. No. 3,950,173 to Ross et al are useful as recording media on which information can be recorded in the form of a relief pattern. Such media, when exposed to a modulated light beam or to an electron beam pattern, change their solubility characteristics in those areas struck by the light or electron beam. Photoresists may be developed by contacting them after exposure with a solvent which dissolves the more soluble portions, leaving the less soluble portions. The resultant relief pattern corresponds to the information contained in the light beam or electron beam. Negative photoresists are initially soluble in the developer solution and the exposed portions become insolubilized. Positive photoresists are initially insoluble and become more soluble in the exposed portions.
It has been found, however, that microscopic areas of these photoresists do not undergo a sufficient change in solubility upon light or electron beam exposure, with the result that the relief pattern formed by contact with a developer solution is imperfect.
When these photoresists are used for recording audio and video information in a manner described in U.S. Pat. No. 3,842,217 to Clemens, the areas that are not developable will result in loss of information. Additionally, the stylus that is used as a capacitance probe will be worn and damaged by contacting these areas and will further damage the playback media. These undevelopable areas have also hindered the use of these photoresists for other applications such as forming integrated circuits. It has been sought to reduce both the number and size of these undevelopable areas.